The invention is a sealed reed contact that is more particularly described as a contact having tapered tip reeds.
A sealed reed contact typically includes a capsule enclosing a pair of magnetic reeds. The reeds are sealed into the capsule so that one end of each reed is fixed, or immobile, and the other end of each reed is free to move. The movable ends of the reeds are positioned to overlap with one another so that they can be moved together for closing a circuit or moved away from each other to open the circuit. Either remanent or non-remanent magnetic material can be used for the reeds.
Because sealed reed contacts are used extensively in telephone switching systems, those contacts occupy a substantial portion of the space allotted for such a system. If the size of the sealed contacts were reduced, considerably space could be saved in all systems installations using a large number of the contacts.
To miniaturize reed contacts, it is desirable to reduce the length of the reeds while retaining the same reed stiffness. This can be accomplished by reducing the thickness of the reed and the diameter of the magnetic wire. Reduction of the diameter decreases the cross-sectional area of the reed, thereby reducing magnetic flux carried by the wire.
An important parameter of operating contacts is the magnetic force of attraction between the two reeds. This force is directly proportional to the square of the magnetic flux and is inversely proportional to the overlap area. In order to retain the closure force of a miniaturized contact at a magnitude equivalent to the magnitude of the larger prior art reed contacts, it is expedient to reduce the overlap area of the miniaturized contact and thereby offset the effect of the reduced flux.
Although reducing the overlap length can reduce the overlap area, the shorter overlap length causes substantial changes in magnetic attraction as a function of variations in the overlap length and misalignment of the reeds.